Hypertonic intranasal vaccines gain nasal epithelia access to exert strong immunogenicity

Intranasal vaccines potentially offer superior protection against viral infections compared with injectable vaccines. The immunogenicity of intranasal vaccines including adenovirus vector (AdV), has room for improvement, while few options are available for safe execution. In this study, we demonstrate that modifying a basic parameter of vaccine formulation, i.e., osmolarity, can significantly enhance the immunogenicity of intranasal vaccines. Addition of glycerol to AdV intranasal vaccine solutions, unlike other viscous additives, enhanced systemic and mucosal antibodies as well as resident memory T cells in the nasal tissues, which could protect nasal tissue and the lungs against influenza virus. While viscous glycerol could not prolong intranasal retention of solutes, it promoted AdV infection of nasal epithelial cells by facilitating AdV access to the nasal epithelial cell. The enhanced immunogenicity was induced by the hypertonicity of vaccine preparations and sodium chloride, glucose, and mannitol demonstrated the capacity to enhance immunogenicity. Moreover, hypertonic glycerol enhanced the immunogenicity of adjuvanted subunit intranasal vaccines, but not subunit vaccines without adjuvant or injectable vaccines. Overall, the delivery of intranasal vaccines to nasal epithelial cells could be improved through a simple approach, potentially resulting in stronger immunogenicity for certain vaccines.